The invention is related to methods and apparatus for separating a fluid into components, and for washing or deglycerolizing a material. The invention is particularly useful for separating whole blood into components and for washing or deglycerolizing separated red blood cells.
Most existing devices for separating a fluid into components utilize a centrifuge to separate heavier components from lighter ones. For instance, U.S. Pat. No. 5,141,645 to Shiraki et al., the disclosure of which is hereby incorporated by reference, describes a blood separation method utilizing a centrifuge. In this system, whole blood is collected in a flexible bag, and the bag is then subjected to a centrifuging operation that causes the heavier blood components (such as red blood cells) to settle at the bottom of the bag. After centrifuging, the lighter blood components, such as plasma and platelets, are drawn off the top of the bag and conducted to a separate container, and the heavier components are left behind in the bag.
Existing systems for separating components of whole blood require multiple separate centrifuging steps. Typically, whole blood in a first container is inserted in a centrifuge and separated into red blood cells and platelet rich plasma in a first centrifuging operation. The centrifuge is then stopped, the first container is removed from the centrifuge, and the platelet rich plasma is separated from the red blood cells and placed in a second container. The second container, and the platelet rich plasma, are then placed in the centrifuge and subjected to a second centrifuging operation that separates the platelets from platelet poor plasma. The centrifuge is again stopped, the second container is removed from the centrifuge, and the platelet poor plasma is separated from the platelets and placed in a third container. These existing methods of separating whole blood are labor intensive and time consuming. As a result, the separation procedures are relatively expensive to perform.
It is also desirable to wash separated red blood cells to fully remove plasma and platelets prior to storage of the red blood cells. Washed red blood cells can be stored at refrigeration temperatures for much longer periods of time than un-washed red blood cells. Unfortunately, the cost of performing a washing procedure using conventional apparatus is relatively high. As a result, washing of red blood cells is not typically performed.
In addition, in a similar procedure, thawed red blood cells that have been stored in a cryoprotective glycerol solution must be washed to remove the glycerol prior to transfusing the red blood cells into a subject. The cost of performing the deglycerolization procedure is an obstacle to use of thawed red blood cells.
In one type of red blood cell washing/deglycerolizing device, a wash solution is introduced into a container holding the red blood cells, and the solution is mixed with the red blood cells to accomplish washing. The container is then subjected to a centrifuging operation to cause the red blood cells to collect on the bottom of the container. The used wash/deglycerolization solution is drawn off the top of the container, leaving washed/deglycerolized red blood cells on the bottom of the container.
Other washing/deglycerolizing devices user a cylindrical chamber that is rotated to force washed red blood cells against the exterior walls of the cylindrical chamber. The wash/deglycerolization solution can then be drained from the cylinder along the axis of rotation. Such red blood cell washing devices incorporate rotating seals that permit introduction and removal of the wash solution. As a result, such systems are relatively complex and expensive, and can be costly to operate because the rotating seals must be replaced after each use.
Another type of red blood cell washing device under investigation utilizes cross-flow filtration. These devices, however, are even more expensive to operate than the centrifuging apparatus described above.